1. Field of the Invention
This invention relates to a synchronizer ring which is adapted for use in transmissions of vehicles which require high torques.
2. Description of the Prior Art
As is known in the art, synchronizer rings have been usually fabricated using only a wear-resistant copper alloy. With the transmissions of vehicles, such as large-sized vehicles or sport cars, which need high power and high torque, the synchronizer ring has been fabricated wherein a synchronizer ring body is made of an iron material and a wear-resistant film or layer is formed on the surface of a sliding portion of the ring body. By this, a high wear resistance is imparted to the sliding portion of the synchronizer ring. This has been realized in the following manner.
1. Mo which is known to have a high wear resistance is spray-coated at a sliding portion. PA1 2. A mixture of a wear-resistant aluminum alloy and Mo is spray-coated at a sliding portion. PA1 3. A wear-resistant part is bonded to a sliding portion mechanically or by welding.
The Mo spray-coating procedure has been widely performed at present for application to large-sized vehicles. However, Mo is very expensive, resulting in the high production costs of the ring article.
The spray-coating of a mixture of a wear-resistant aluminum alloy and Mo has now been used in some synchronizer rings. This is because Si contained in the wear-resistant aluminum alloy is liable to impede wettability with a matrix body on spray-coating, thereby lowering the bonding strength of the coated film. In fact, limitation is placed on the applications except for large-sized vehicles.
With wear-resistant parts being bonded mechanically or by welding, a wear-resistant part has a sliding surface shaped in the form of a ring and inserted into a synchronizer ring body. Thereafter, the part may be fixed with a pin. Alternatively, the part may be subjected to a complicated procedure of the combination of shrink fitting, cold fitting and electron beam welding. Thus, the fabrication becomes very complicated. In addition, an increasing number of parts are essential with an additional number of assembling steps, thus leading to an inconvenience from the standpoint of production costs.